constructor(x, y) {

    this.x = x;

    this.y = y;

  }

  draw() {

    strokeWeight(5);

    point(O[0] + this.x * sX, O[1] - this.y * sY);

    strokeWeight(1);

  }

}

class fun {

  constructor(a, b) {

    this.a = a;

    this.b = b;

  }

  value(x) {

    return this.a * x + this.b;

  }

  graph(a, b) {

    a = a || -O[0] / sX;

    b = b || (w - O[0]) / sX;

    line(

      O[0] + a * sX, //O[0]+a-O[0])*

      O[1] - this.value(a) * sY,

      O[0] + b * sX,

      O[1] - this.value(b) * sY

    );

  }

  reg(a) {

    if (a.length > 1) {

      let sX = 0;

      let sY = 0;

      let sXY = 0;

      let sXX = 0;

      for (let i = 0; i < a.length; i++) {

        sX += a[i].x;

        sY += a[i].y;

        sXY += a[i].x * a[i].y;

        sXX += sq(a[i].x);

      }

      this.a = (a.length * sXY - sX * sY) / (a.length * sXX - sq(sX));

      this.b = (sXX * sY - sX * sXY) / (a.length * sXX - sq(sX));

    }

  }

  res(a) {

    let b = [];

    for (let i = 0; i < a.length; i++) {

      b.push(a[i].y - this.value(a[i].x));

    }

    return b;

  }

  rSq(a) {

    let Sr = 0;

    let Sy = 0;

    let My = 0;

    for (let i = 0; i < a.length; i++) {

      Sy += a[i].y;

    }

    My = Sy / a.length;

    Sy = 0;

    for (let i = 0; i < a.length; i++) {

      Sr += sq(this.res(a)[i]);

      Sy += sq(a[i].y - My);

    }

    return 1 - Sr / Sy;

  }

}

​

function mousePressed() {

  mX = mouseX;

  mY = mouseY;

}

function mouseReleased() {

  dX = mouseX - mX;

  dY = mY - mouseY;

  if (keyIsDown(16)) {

    sX = sX * pow(1.01, dX);

    O[0] = (w / 2) * (1 - pow(1.01, dX)) + O[0] * pow(1.01, dX);

    sY = sY * pow(1.01, dY);

    O[1] = (h / 2) * (1 - pow(1.01, dY)) + O[1] * pow(1.01, dY);

  } else {

    O[0] += mouseX - mX;

    O[1] += mouseY - mY;

  }

}

let xIn;

let yIn;

let uXin;

let uYin;

let P = [];

let eP = [];

let pP = [];

let f = new fun(1, 0);

let sXm = 0;

let sYm = 0;

let e = 0;

let p = 0;

let nE = 0;

let nP = 0;

let tX = 40;

let tY = 0;

let t1w = 50;

let t2w = 40;

let m = 20;

let PmiX;

let PmaX;

let w = 900;

let h = 750;

let O = [w / 2, h / 2];

let sX = 1;

let sY = 1;

let rP = 200;

function setup() {

  createCanvas(w, h + rP);

  xIn = createInput("");

  xIn.position(tX, tY + 2 * m);

  xIn.size(t1w);

  yIn = createInput("");

  yIn.position(tX, tY + 20 + 2 * m);

  yIn.size(t1w);

  uXin = createInput("");

  uXin.position(tX + t1w, tY + 2 * m);

  uXin.size(t2w);

  uYin = createInput("");

  uYin.position(tX + t1w, tY + 20 + 2 * m);

  uYin.size(t2w);

}

function draw() {

  background(220);

  textSize(20);

  text("Funktionsforskriften er", tX + t1w + t2w + 10, tY + 20 + 2 * m);

  if (keyIsDown(13) && xIn.value() != "" && yIn.value() != "") {

    P.push(new cPoint(float(xIn.value()), float(yIn.value())));

    f.reg(P);

    PmiX = min(PmiX, float(xIn.value()));

    PmaX = max(PmaX, float(xIn.value()));

    xIn.value("");

    yIn.value("");

  }

  if (keyIsDown(69)) {

    e = 1;

    p = 0;

    while (nE < P.length) {

      eP.push(new cPoint(P[nE].x, log(P[nE].y)));

      nE++;

    }

    f.reg(eP);

  }

  if (keyIsDown(80)) {

    p = 1;

    e = 0;

    while (nP < P.length) {

      pP.push(new cPoint(log(P[nP].x), log(P[nP].y)));

      nP++;

    }

    f.reg(pP);

  }

  if (keyIsDown(76)) {

    e = 0;

    p = 0;

    f.reg(P);

  }

  if (e == 1) {

    for (let i = 0; i < eP.length; i++) {

      eP[i].draw();

      text(

        "(" + round(eP[i].x, 2) + "," + round(eP[i].y, 2) + ")",

        tX,

        tY + 20 * (i + 3) + 2 * m

      );

    }

    text(

      "f(x)=" + round(exp(f.b), 2) + "⋅" + round(exp(f.a), 2) + "^x",

      tX + t1w + t2w + 10,

      tY + 40 + 2 * m

    );

  } else if (p == 1) {

    text(

      "f(x)=" + round(exp(f.b), 2) + "x^" + round(f.a, 2),

      tX + t1w + t2w + 10,

      tY + 40 + 2 * m

    );

    for (let i = 0; i < pP.length; i++) {

      strokeWeight(5);

      pP[i].draw();

      text(

        "(" + round(pP[i].x, 2) + "," + round(pP[i].y, 2) + ")",

        tX,

        tY + 20 * (i + 3) + 2 * m

      );

    }

  } else {

    for (let i = 0; i < P.length; i++) {

      P[i].draw();

      text("(" + P[i].x + "," + P[i].y + ")", 2 * m, 2 * m + 20 * (i + 3));

      strokeWeight(5);

      point(

        m + ((w - 2 * m) / (PmaX - PmiX)) * (P[i].x - PmiX),

        h +

          rP / 2 -

          (((rP - m) / max(max(f.res(P)), -min(f.res(P)))) * f.res(P)[i]) / 2

      );

      strokeWeight(1);

    }

    text(

      "f(x)=" + round(f.a, 2) + "x+" + round(f.b, 2),

      tX + t1w + t2w + 10,

      tY + 40 + 2 * m

    );

    text("r^2=" + f.rSq(P), tX + t1w + t2w + 10, tY + 60 + 2 * m);

    line(0, h + rP / 2, w, h + rP / 2);

  }

  strokeWeight(1);

  text(

    "(" +

      round((m - O[0]) / sX, 1) +

      "," +

      round((O[1] - h + 20) / sY, 1) +

      ")",

    30,

    h - m - 10

  );

  textAlign(RIGHT);

  text(

    "(" + round((w - m - O[0]) / sX, 1) + "," + round((O[1] - m) / sY, 1) + ")",

    w - m - 10,

    m + 20

  );

  f.graph();

  if (O[0] < m) {

    stroke(150);

    line(m, 0, m, h);

    stroke(0);

    text(uYin.value(), m + 10, m + 5);

  } else if (O[0] > w - m) {

    stroke(150);

    line(w - m, 0, w - m, h);

    stroke(0);

    textAlign(RIGHT);

    text(uYin.value(), w - 3 * m, m + 5);

    textAlign(LEFT);

  } else {

    stroke(0);

    line(O[0], 0, O[0], h);

    text(uYin.value(), O[0] + 5, m + 5);

  }

  stroke(150);

  if (O[1] > h - m) {

    line(0, h - m, w, h - m);

    stroke(0);

    textAlign(RIGHT);

    text(uXin.value(), w - m + 5, h - 3 * m);

    textAlign(LEFT);

  } else if (O[1] < m) {

    line(0, m, w, m);

    stroke(0);

    textAlign(RIGHT);

    text(uXin.value(), w - m + 5, 2 * m + 10);

    textAlign(LEFT);

  } else {

    stroke(0);

    line(0, O[1], w, O[1]);

    textAlign(RIGHT);

    text(uXin.value(), w - m + 5, O[1] - m * 0.5);

    textAlign(LEFT);

  }

  stroke(150);

  line(m, 0, m, h);

  line(w - m, 0, w - m, h);

  line(0, m, w, m);

  line(0, h - m, w, h - m);

  stroke(0);

}

​